A metal-oxide-semiconductor (MOS) transistor is one of the most important devices in modern integrated circuits. A MOS transistor usually includes a semiconductor substrate, gate structures on a surface of the semiconductor substrate, and source/drain regions in the semiconductor substrate on both sides of each gate structure. Each gate structure further includes a gate dielectric layer on the surface of the semiconductor substrate and a gate electrode layer on a surface of the gate dielectric layer.
With continuous developments of the semiconductor technology, the conventional planar CMOS transistors have a worse controlling ability on the channel current, inducing serious leakage current problems. A fin field effect transistor (FinFET) is one emerging multi-gate device. A typical structure of a FinFET usually includes fins protruding from the semiconductor substrate, gate structures covering a portion of top surfaces and sidewalls of the fins, and source/drain regions in the fins on both sides of each gate structure.
However, the performance of conventionally fabricated FinFET devices still needs to be improved. The disclosed devices and methods are directed to at least partially alleviate one or more problems set forth above and to solve other problems in the art.